Dual clutch mechanisms typically have a single input shaft that, through a pair of selectively engageable plate clutch mechanisms, drives one of a pair of output shafts for rotation. One example of such an arrangement uses an input shaft positioned within a hollow inner output shaft, which in turn is positioned within a hollow outer output shaft.
Such dual clutch mechanisms typically have a first clutch arrangement which has a driven side and a driving side, along with a second clutch arrangement which also has driven side and a driving side. The selective activation of either of the first and second clutch arrangements allows for the input shaft to drive one of the inner and outer output shafts. The driven side the first and second clutch arrangements is driven for rotation via the input shaft, which is disposed within both the inner and outer output shafts. The driving side of the first clutch arrangement selectively drives one of the inner and outer output shafts for rotation, while the driving side of the second clutch arrangement selectively drives the other of the inner and outer output shafts for rotation.
Dual clutch mechanisms can be used in automotive transmission systems, such as for shifting between gears in an automatic transmission. A consideration in configuring a dual clutch mechanism for a particular automobile can be the size of the mechanism, and in particular the overall radial extent of the mechanism. In general, a reduced overall radial extent of the dual clutch mechanism can beneficially provide for greater flexibility in its arrangement within an automobile. Another consideration in configuring a dual clutch mechanism for a particular automobile can be the size and torque capacity of the gear selectors, such as synchronizers, for engaging gears with the output shafts of the dual clutch transmissions. The size and capacity of the gear selectors is determined in part by the forces imparted to the output shafts by the dual clutch mechanism. In general, the more torque capacity that is required of the synchronizer, the larger and more costly the synchronizer is.
The clutch mechanisms can include a plurality of annular discs associated with the driven side of each of the clutches intermeshed with a plurality of annular discs associated with the driving side of each of the clutches. The intermeshed discs are selectively engageable to permit the driven side of the clutch to drive the driving side of the clutch for rotation.
Typically the driven or input side of the clutch arrangements are driven for rotation via driven plates connected to inner diameters of the annular driven discs and the driving or output side of the clutch arrangements drive driving plates connected to outer diameters of the annular driving discs. Such a driving path via the radially outward diameters of the clutch arrangements can result in a large rotational inertia which must be overcome to accelerate the driving plates to the same speed as the intermeshed driven plates. The required forces to overcome the rotational inertia associated with having the driving plates of the clutch arrangements connected via the radially outward diameter of the clutch arrangements can adversely impact the ability to rapidly shift between gears associated with different output shafts by increasing the time require to accelerate the driving discs to the same speed as the driven discs, and can require increased capacity synchronizers.
Fluid is supplied to intermeshed driving and driven discs to permit cooling and/or lubrication during their frictional engagement. However, fluid is also typically also supplied to the driving and driven discs when unengaged. Switching from transmitting torque with one of the output shafts associated with a lower effective gear ratio to transmitting torque with the other of the output shafts associated with a higher effective gear ratio involves first accelerating the other of the output shafts prior to engagement of the driving and driven discs of that output shaft. Clutch drag due to fluid between the unengaged driving and driven discs as well as other components can slow the acceleration of the driving discs in the unengaged set of discs prior to their engagement, thereby decreasing the response time of the dual clutch mechanism and requiring synchronizers having a greater torque capacity to overcome the clutch drag in the dual clutch mechanism.
Dual clutch mechanisms can have the first and second clutch arrangements positioned parallel to each other along the principle axis of rotation of the clutch mechanism. An example of a parallel dual clutch mechanism is disclosed in EP1195537. As shown in the '537 publication, however, the output shafts often are driven via the outer diameters of the driving discs of the clutch arrangements.
Accordingly, it is desired to provide a dual clutch mechanism that provides flexibility in the design, installation, and selection of both the dual clutch mechanism itself and transmission components, such as synchronizers, installed within the engine compartment. In particular, it is desired to provide a dual clutch mechanism that is reduced in cost and can operate with a reduced complexity of design constrictions.